1. Technical Field
The present invention generally relates to a developing device used in electrophotographic image formation and to a process cartridge and an image forming apparatus, such as, a copier, a printer, a facsimile machine, a plotter, or a multifunction peripheral (MFP) or multifunction machine having at least two of coping, printing, facsimile transmission, plotting, and scanning capabilities, that includes the developing device.
2. Description of the Background Art
In electrophotographic image forming apparatuses, such as copiers, printers, facsimile machines, or multifunction machines, low-temperature image fixing is promoted to reduce impact on environment. Accordingly, there is an increasing possibility that developer (i.e., toner) coagulates inside a toner bottle, a toner replenishing device, or a developing unit when the temperature therein rises during image forming operation or it is left under hot and humid conditions.
When scooped onto a developing sleeve and used in image development, the coagulated developer (i.e., aggregates) results in substandard images including image failure such as spots, shooting star marks, white lines, or the like. To prevent spots, shooting star marks, white lines, or the like, for example, the following approaches have been tried.
1. Use moisture-proof packaging materials to prevent developer coagulation in toner bottles left for a long time under hot and humid conditions;
2. Use ball bearings having a good slidability or metal shaft screws to prevent developer coagulation caused by temperature rise when the developing unit is operated consecutively;
3. Increase image output intervals to cool the apparatus when the temperature inside the apparatus reaches a threshold;
4. Rotate a developer bearer in reverse to loosen coagulated developer stuck between the developer bearer and a developer regulator (see JP-2010-204343-A).
Further, JP-2007-264105-A proposes providing a filter in a communicating portion between two developer conveyance channels that are parallel to each other at least in a certain range. The filter can be a mesh having mesh openings that are three times to twenty times greater in size than toner particles, and aggregates can be loosened by filtering.